1. Field of the Invention
The present invention relates, for example, to a communication system suitable for being applied to an apparatus constituted by a communication terminal apparatus such as a mobile telephone terminal and a wireless key apparatus restricting the operation of the communication terminal apparatus and to a communication terminal apparatus and a wireless key apparatus constituting the communication system.
2. Description of the Related Art
In recent years, a mobile telephone terminal which is one of communication terminal apparatuses a user always taking along in possession has a trend such that various functions other than wireless telephone functions of primary functions are built-in so as to contain multi functions.
For example, there exists such a terminal in which a camera function carrying out a filming of a still picture and a moving picture, a recording and reproducing function of music data, a viewing and listening function of television broadcast or the like is built-in.
In addition, there has been developed a mobile telephone terminal in which a function as a non-contacting IC card which has been prevailing rapidly in recent years is built-in. This non-contacting IC card is utilized as a boarding ticket of transport facilities, a membership card, an employee ID card, a card for price settlement means at a shop or the like where an authentication process is carried out by performing wireless communication between adjacent reader and writer, so that it is easy-to-use as compared with a magnetic card or the like. It should be noted in a case when an IC card function unit is mounted in a mobile terminal that the IC card function unit is not always necessarily to have a card type shape.
And now, it is preferable for the mobile telephone terminal having multi functions in this manner to be carried out with a process in order to secure some kind or another security for preventing various functions provided in the terminal from being abused when the terminal is lost. In particular, in case of a terminal installed with an IC card function unit, there is a possibility that personal information stored as the IC card function is read out unjustly or unjust settlement or the like utilizing the IC card function is carried out, so that the necessity for a function for preventing the unjust use thereof is high. There are descriptions, for example, in patent documents 1 and 2 that a wireless card which forms a pair with respect to the mobile telephone terminal is prepared and authentication request is wireless-transmitted periodically from that wireless card such that the functions of mobile telephone terminal is made to be restricted in a case when collation with respect to the authentication request cannot be taken.
[Patent Document 1] Jap. laid-open patent publication No. 2001-352579
[patent document 2] Jap. laid-open patent publication No. 2001-358827
However, if it is attempted to provide in a mobile telephone terminal with a communication circuit for carrying out an exclusive authentication process or authentication processing means for carrying out function limitation of that terminal such as shown in the descriptions in the patent documents 1 and 2, there is a problem that the constitution of the terminal becomes complicated. In case of carrying out such a wireless communication for the function limitation, if various wireless communication systems existing in the related art can be applied as they are, it is to contribute to lowering the cost of a mobile terminal.
However, in a case when it is considered to use various wireless communication systems existing in the related art as they are for the purpose of security assuring, a case is supposed in which the function limitation does not always function effectively. More specifically, it is fundamental for a commonly used wireless communication system to carry out a wireless communication with a terminal of a partner as favorably as possible within the specification given by the wireless system. Consequently, for example, a wireless card for carrying out function limitation of a mobile telephone terminal and its terminal is prepared and even if a system is composed assuming that the function of the mobile telephone terminal is made to be limited in a case when the distance between the both sides becomes apart equal or more than around several meters, it is practically difficult to define one-sidedly a distance which makes the wireless communication possible between the mobile telephone terminal and the wireless card such that it is supposed that there were various problems for making it practicable. More specifically, in case of a favorable communication environment, the function limitation is made effective after a quite far distance and in case of an inferior communication environment on the contrary, the wireless communication cannot be carried out even if the mobile telephone terminal and the wireless card are adjacent and the function limitation is made effective.
Also, it is preferable for an apparatus such as a wireless card or the like which is used as a pair with a mobile telephone terminal not to take a lot of trouble as much as possible for everyday use, but practically, relatively a large power consumption occurs when it always exchanges data for authentication or the like with a mobile telephone terminal, so that it is frequently necessary to exchange or charge a battery and there was a problem that it took a lot of trouble for functioning it as an authentication apparatus.